Permanent Genetic Resources added to the Molecular Ecology Resources Database 1 February 2010-31 March 2010.

This article documents the addition of 228 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anser cygnoides, Apodemus flavicollis, Athene noctua, Cercis canadensis, Glis glis, Gubernatrix cristata, Haliotis tuberculata, Helianthus maximiliani, Laricobius nigrinus, Laricobius rubidus, Neoheligmonella granjoni, Nephrops norvegicus, Oenanthe javanica, Paramuricea clavata, Pyrrhura orcesi and Samanea saman. These loci were cross-tested on the following species: Apodemus sylvaticus, Laricobius laticollis and Laricobius osakensis (a proposed new species currently being described).

MK-801 disrupts acquisition of contextual fear conditioning but enhances memory consolidation of cued fear conditioning.

The effects of pre-training or post-training subcutaneous injections of multiple doses of the non-competitive NMDA-receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) on cued and contextual fear conditioning were examined in F344 rats. Pre-training injections of MK-801 (0.3 and 1.0 mg/kg) disrupted contextual fear conditioning but not cued fear conditioning. Post-training injections of MK-801 did not disrupt cued or contextual fear conditioning. In fact, the 0.3 mg/kg dose of MK-801 enhanced cued fear conditioning. Finally, rats were tested for MK-801-induced alterations in sensitivity to pain using the formalin test for nociception. MK-801 did not reduce sensitivity to pain. These results suggest that NMDA receptors are involved in acquisition of contextual fear conditioning but not in memory consolidation of the learned response.

Differential sensitivity to lithium's reversal of amphetamine-induced open-field activity in two inbred strains of mice.

To determine whether genetic differences could contribute to the pharmacological sensitivity of lithium chloride (LiCl) to reverse amphetamine-associated changes in behavior C57BL/6nCrlBR and C3H/HenCrlBR male mice were tested for the ability of an acute dose of LiCl to reverse the locomotor enhancing effects of an acute dose of amphetamine. A series of experiments were conducted that compared dose response of LiCl, chamber lighting conditions, and chamber shape on amphetamine-induced activity in two strains of mice with different genetic backgrounds. Acute amphetamine (3 mg/kg) increased locomotor activity in C57BL/6nCrlBR mice and LiCl (1-4 mEq/kg) blocked this effect. LiCl-induced changes in baseline activity seen at high doses of LiCl were not seen for the low doses. The dark condition reduced time resting but chamber shape did not appear to alter results. In C3H/HenCrlBR mice, amphetamine did not significantly increase levels of activity but did decrease rearing behavior which suggests that genetic difference between C57BL/6nCrlBR and C3H/HenCrlBR mice may contribute to sensitivity to amphetamine. In sum, the ability of LiCl to reverse amphetamine-induced changes in locomotor activity in C57BL/6nCrlBR mice may provide a useful model to study genetic and pharmacological aspects of psychiatric illnesses such as bipolar disorder.

Regulation and localization of tyrosine216 phosphorylation of glycogen synthase kinase-3beta in cellular and animal models of neuronal degeneration.

Inactivation of glycogen synthase kinase-3beta (GSK3beta) by S(9) phosphorylation is implicated in mechanisms of neuronal survival. Phosphorylation of a distinct site, Y(216), on GSK3beta is necessary for its activity; however, whether this site can be regulated in cells is unknown. Therefore we examined the regulation of Y(216) phosphorylation on GSK3beta in models of neurodegeneration. Nerve growth factor withdrawal from differentiated PC12 cells and staurosporine treatment of SH-SY5Y cells led to increased phosphorylation at Y(216), GSK3beta activity, and cell death. Lithium and insulin, agents that lead to inhibition of GSK3beta and adenoviral-mediated transduction of dominant negative GSK3beta constructs, prevented cell death by the proapoptotic stimuli. Inhibitors induced S(9) phosphorylation and inactivation of GSK3beta but did not affect Y(216) phosphorylation, suggesting that S(9) phosphorylation is sufficient to override GSK3beta activation by Y(216) phosphorylation. Under the conditions examined, increased Y(216) phosphorylation on GSK3beta was not an autophosphorylation response. In resting cells, Y(216) phosphorylation was restricted to GSK3beta present at focal adhesion sites. However, after staurosporine, a dramatic alteration in the immunolocalization pattern was observed, and Y(216)-phosphorylated GSK3beta selectively increased within the nucleus. In rats, Y(216) phosphorylation was increased in degenerating cortical neurons induced by ischemia. Taken together, these results suggest that Y(216) phosphorylation of GSK3beta represents an important mechanism by which cellular insults can lead to neuronal death.

A one year-review of anti-epileptic drug monitoring in Trinidad

OBJECTIVE: To audit anti-epileptic drug monitoring in tertiary hospitals in Trinidad. METHODS: Epileptic patients, from hospital clinics, who were receiving maintenance therapy and were referred for plasma drug level monitoring, gave informed consent and were enrolled. Blood collection was at trough levels of drug and coded plasma samples were analysed by competitive immunoassay on the TDx Monitoring system. RESULTS: All 93 patients consented to participate. Phenytoin and carbamazepine were the two major drugs prescribed. The use of multiple drugs did not influence the occurrence of seizures in the patients; (31 percent) receiving polytherapy. Phenobarbital was the most frequent agent added to the drug regime in 24/9 patients (83 percent). Low plasma levels of drugs were detected in 58 percent and 36 percent of patients receiving polytherapy with phenytoin and carbamazepine respectively; but an association was not found between the range of drug levels and the frequency of seizures. Seventy-seven (83 percent) patients reported good compliance. Plasma drug levels were significantly below normal (p=0.004) in patients who reported poor compliance. CONCLUSIONS: Multiple drug therapy did not influence the prognosis of seizure control in this study. Suspected non-compliance, drug toxicity and failure to individualize dosing are considerations for plasma level drug monitoring in the protocol for management of epilepsy.(Au)

Facilitating patient learning during medical rehabilitation: a research agenda.

Although patient learning is widely acknowledged to be an integral part of many medical rehabilitation practices, it has been the subject of little systematic research. A workshop conducted August 18 to 19, 1997, was organized by the National Center for Medical Rehabilitation Research (National Institute of Child Health and Human Development, National Institutes of Health) and several co-sponsoring organizations to formulate recommendations concerning learning-oriented rehabilitation practices. The recommendations and their supporting rationale are summarized in the topic areas of motor learning and control, cognitive learning, recovery of functioning, generalization and transfer of training, and applications for patients with strokes, traumatic brain injury, amputations, and infants and children.

Patient satisfaction and rehabilitation services.

OBJECTIVE: Despite the widespread use of patient satisfaction measures, there has been only a small amount of research and writing on the topic in rehabilitation. This article reviews selectively the large amount of literature on satisfaction in health care, examines work in rehabilitation settings, and highlights issues in patient satisfaction, given the unique circumstances of rehabilitation services. DATA SOURCES: A Medline search was made of the past 10 years using descriptors related to patient satisfaction, rehabilitation, and selected diagnostic categories. Additional sources came from references on satisfaction accumulated by the author over the past 20 years. STUDY SELECTION: Because of the voluminous literature, findings from existing reviews were emphasized, particularly those using meta-analytic methods. All articles that involved satisfaction in rehabilitation settings were included. DATA SYNTHESIS: Research in health care generally shows high levels of satisfaction. Personal aspects of care, including full communication, are the most important predictors, whereas age, education, and social status show weak relationships with rating levels. Dissatisfied patients tend to seek other providers. Higher satisfaction is associated with patient compliance and better outcomes. Levels of satisfaction are especially high in rehabilitation. CONCLUSIONS: Measures of patient satisfaction with rehabilitation should include items regarding progress and degree of return to independent living. Responses of proxies answering in place of patients should not be regarded as equivalent to patients' opinions. The field is in need of standard, validated measures appropriate for various settings.

Treatment strength in rehabilitation.

OBJECTIVE: To propose treatment strength as central to an understanding of rehabilitation treatment, to delineate its features, to examine related research, and to suggest ways to improve the specification and conceptualization of treatment. DATA SOURCES: Published literature. STUDY SELECTION: Definitions were proposed for treatment strength components: purity, specificity, dose, intensity, duration, timing, and treater characteristics and organization. Three measures of treatment exposure were selected as having the most research: length of inpatient stay, treatment intensity, and treatment specificity (using as example the stroke rehabilitation unit). Length of stay information was selected primarily from studies using multifacility data systems. All studies identified as using greater treatment intensity or augmented treatment were selected. Because of the large literature on stroke units, selected studies were chosen that used randomized controlled trials or community-based data. RESULTS: Greater treatment exposure, as measured by length of stay, generally results in greater benefit, although there are wide variations for a given condition over time and across countries. Research on treatment intensity uses various definitions for intensity with mixed results. Specialization, in the form of the stroke rehabilitation unit, generally produces superior outcomes than other types of care, although there is little investigation of the reasons for benefit. CONCLUSIONS: Understanding of rehabilitation treatment would be improved by (1) routinely reporting hours of service by discipline, (2) using treatment strength concepts, (3) analyzing the relation of naturally occurring variations of treatment strength to outcomes, and (4) developing a taxonomy of treatment types.

Voltage-dependent inhibition of N- and P-type calcium channels by the peptide toxin omega-grammotoxin-SIA.

We studied the mechanism by which the peptide omega-grammotoxin-SIA inhibits voltage-dependent calcium channels. Grammotoxin at concentrations of > 50 nM completely inhibited inward current carried by 2 mM barium through P-type channels in rat cerebellar Purkinje neurons when current was elicited by depolarizations up to +40 mV. However, outward current (carried by internal cesium) elicited by depolarizations to > +100 mV was either unaffected or enhanced in the presence of toxin. Tail current activation curves showed that grammotoxin shifted the steady state voltage dependence of channel activation by approximately +40 mV. Activation in the presence of toxin was far slower in addition to having altered voltage dependence. Grammotoxin also inhibited N-type calcium channels in rat and frog sympathetic neurons, with changes in channel voltage dependence and kinetics nearly identical to those of P-type channels. Experiments with monovalent ions as the only charge carriers showed that toxin effects on channel activation and kinetics depended on voltage, not on direction of current flow or on the current-carrying ion. Repeated trains of large depolarizations relieved toxin inhibition, as if toxin affinity for activated channels were low. The effects of grammotoxin on gating of P-type channels are very similar to those of omega-Aga-IVA, but combined application of the two toxins showed that grammotoxin binding is not prevented by saturating binding of omega-Aga-IVA. We conclude that grammotoxin potently inhibits both P-type and N-type channels by impeding channel gating and that grammotoxin binds to distinct or additional sites on P-type channels compared with omega-Aga-IVA.

Complete and reversible block by omega-grammotoxin SIA of glutamatergic synaptic transmission between cultured rat hippocampal neurons.

omega-Grammotoxin SIA (omega-GsTx SIA), a peptide isolated from tarantula venom, inhibits synaptosomal Ca2+ influx and neurotransmitter release, and blocks N-, P-, and Q-type voltage-gated Ca2+ channels. The whole-cell patch-clamp was used to record glutamatergic excitatory post-synaptic currents (EPSCs) evoked by extracellular stimulation of presynaptic neurons in primary rat hippocampal cultures. EPSCs displayed rapid kinetics and were blocked by CNQX. omega-Conotoxin (1 microM) GVIA inhibited EPSCs by 46%, while 30 nM and 1 microM omega-agatoxin IVA produced 12% and 69% inhibition, respectively, consistent with coupling of N-, P- and Q-type Ca2+ channels to glutamatergic synaptic transmission. omega-GsTx SIA (1 microM) rapidly, completely, and reversibly blocked glutamatergic EPSCs, but did not affect currents evoked by bath application of kainate. Thus, omega-GsTx SIA blocks glutamatergic synaptic transmission by blocking presynaptic voltage-gated Ca2+ channels. omega-GsTx SIA is the only agent that blocks selectively and reversibly the Ca2+ channels coupled to glutamate release. omega-GsTx SIA provides a unique and powerful tool for experiments requiring recovery of function following presynaptic block of synaptic transmission.

Comparative actions of synthetic omega-grammotoxin SIA and synthetic omega-Aga-IVA on neuronal calcium entry and evoked release of neurotransmitters in vitro and in vivo.

The effects of synthetic omega-grammotoxin SIA (omega-GsTxSIA) and synthetic omega-Aga-IVA were tested in in vitro and in vivo neurochemical assays that are reflective of voltage-sensitive calcium channel function. Synthetic omega-GsTx SIA inhibited K(+)-evoked rat and chick synaptosomal 45Ca2+ flux, K(+)-evoked release of [3H]D-aspartate and [3H]norepinephrine from rat hippocampal brain slices and K(+)-evoked release of [3H]norepinephrine from chick cortical brain slices with potency values that were comparable to those found previously with omega-GsTx SIA purified from the venom of the tarantula spider Grammostola spatulata. These results indicate that trace contaminants do not account for the pharmacology of purified omega-GsTx SIA. omega-GsTx SIA caused a complete inhibition of rat synaptosomal 45Ca2+ flux and hippocampal slice [3H]D-aspartate release, whereas omega-Aga-IVA caused a maximal inhibition of approx 75%. omega-GsTx SIA and omega-Aga-IVA caused an identical partial inhibition of K(+)-evoked increases of intracellular calcium in cortical neurons in primary culture. The addition of nitrendipine to either omega-GsTx SIA or omega-Aga-IVA resulted in an additive and virtually complete inhibition of the cortical neuron intracellular calcium response. In in vivo microdialysis studies, the K(+)-evoked release of glutamate from hippocampus of awake freely moving rats was inhibited with the following rank order of potency: omega-conotoxin GVIA > omega-GsTx SIA > omega-Aga-IVA. Complete inhibition of K(+)-evoked hippocampal glutamate release was observed with 300 nM omega-conotoxin GVIA and 3 microM omega-GsTx SIA. In urethane anesthetized rats, omega-CgTx GVIA caused a partial inhibition, whereas omega-GsTx SIA caused a concentration-dependent and complete inhibition, of basal serotonin release in the hippocampus. Therefore, omega-GsTx SIA was shown to inhibit responses that are sensitive to omega-conotoxin GVIA, omega-Aga-IVA and omega-conotoxin MVIIC, consistent with the notion that omega-GsTx SIA inhibits N-, P- and Q-type high threshold voltage-sensitive calcium channels.

Omega-grammotoxin SIA blocks multiple, voltage-gated, Ca2+ channel subtypes in cultured rat hippocampal neurons.

Omega-Grammotoxin SIA is a peptide isolated from tarantula venom on the basis of its ability to block the voltage-gated Ca2+ channels that mediate glutamate release. To determine the Ca2+ channel subtype selectivity of omega-grammotoxin SIA, whole-cell Ba2+ current (IBa) was measured in cultured rat hippocampal neurons. Selective Ca2+ channel blockers were used to identify components of IBa mediated by Ca2+ channel subtypes. omega-Agatoxin IVA at 30 nM, 1 microM omega-conotoxin GVIA, and 3 microM omega-contoxin MVIIC, applied consecutively, each elicited a fractional increase in the cumulative block of IBa, identifying components of IBa mediated by P-, N-, and Q-type calcium channels. omega-Grammotoxin at 1 microM, a maximally effective concentration, blocked 52% of IBa. omega-Conotoxin MVIIC and the combination of omega-conotoxin GVIA and micromolar omega-agatoxin IVA blocked 52% and 54% of IBa, respectively, and block of IBa by omega-grammotoxin SIA was mutually occlusive of block of IBa by either treatment, both of which block N-, P-, and Q-type Ca2+ channels. The L channel blocker nimodipine produced identical block of IBa in the presence and absence of omega-grammotoxin SIA. These results indicate that omega-grammotoxin SIA blocks N-, P-, and Q-type but not L-type voltage-gated calcium channels. Block of IBa by omega-grammotoxin SIA was faster in onset and less sensitive to external divalent cation concentrations than was block by omega-conotoxin MVIIC, and it was rapidly and substantially reversible. Rapid onset, relative insensitivity to divalent cation concentrations, and reversibility render omega-grammotoxin SIA a useful tool for inhibition of neuronal voltage-gated Ca2+ channels.

Acute and subacute rehabilitation for stroke: a comparison.

Subacute rehabilitation, a recent innovation, is a less intense form of traditional inpatient rehabilitation. This study is a retrospective comparison of stroke treatment in a comprehensive inpatient service (acute rehabilitation) and subacute rehabilitation in a skilled nursing facility. Consecutive records during 1990 and 1991 resulted in 331 patients at the acute level and 97 at the subacute. Analysis of patient characteristics found few major differences between the two populations. Scrutiny of billing records found that acute program patients had twice as much treatment during a stay, twice the daily treatment hours, and twice the average charge per day. Acute rehabilitation patients showed substantially greater gains in functional impairment measures (FIM), but the proportion of patients discharged to the community varied little. Cost-effectiveness analysis found that the charge per successful discharge was more than double for acute rehabilitation. The charge per one point of FIM gain also was substantially higher. Although subacute rehabilitation was found to be more cost-effective than acute, additional research is needed to establish policies regarding rehabilitation services.

Conceptual basis of outcome measures.

Because of its treatment configuration and the assumption of long-term benefit, rehabilitation has had a continuing interest in the measurement of outcomes. The utility of outcome indicators rests on their conceptual foundations, the technical development of measures and validation research. Some measures, particularly of functional status, have become increasingly sophisticated with the application of psychometric and statistical analysis techniques. Less effort has been devoted to an elaboration of their theoretical basis. A first step is an examination of the assumptions underlying outcome measures, the purpose of this article. Central to an understanding is clarification of definitions of key terms such as outcomes, independence, impairment, disability and handicap. All outcome measures must be seen as part of a social context of norms and expectations. However, most norms in rehabilitation are implied rather than explicit. The assumptions behind several common outcomes are examined with suggestions for ways to increase their utility. The ability of rehabilitation to compete in the current climate, stressing cost-effectiveness, will depend heavily on the robustness of outcome measures.

Differential inhibition of neuronal calcium entry and [3H]-D-aspartate release by the quaternary derivatives of verapamil and emopamil.

1. Verapamil and emopamil are structurally related phenylalkylamine calcium channel/5-HT2 receptor antagonists that differ in their anti-ischaemic properties in experimental studies. The quaternary ammonium derivatives of these compounds were prepared and tested in assays of neuronal voltage-sensitive calcium channel (VSCC) function to determine whether the compounds act at intra- or extracellular sites. 2. The compounds were tested in K(+)-evoked: (1) rat brain synaptosomal 45Ca2+ influx, (2) release of [3H]-D-aspartate from rat hippocampal brain slices and (3) increase of intracellular calcium in rat cortical neurones in primary culture. 3. Verapamil, emopamil and the emopamil quaternary derivative caused concentration-dependent and comparable (IC50 values approximately 30 microM) inhibition of synaptosomal 45Ca2+ influx and [3H]-D-aspartate release. The verapamil quaternary derivative was considerably less active in these assays (IC50 > 300 microM). 4. The evoked increase of intracellular calcium in cortical neurones was inhibited with the following rank order of potency (IC50 value, microM): emopamil (3.6) > verapamil (17) > emopamil quaternary derivative (38) > verapamil quaternary derivative (200). 5. The results suggest that verapamil and emopamil inhibit nerve terminal VSCC function (synaptosomal 45Ca2+ influx and [3H]-D-aspartate release) by acting at distinct intracellular and extracellular sites, respectively. Verapamil and emopamil may inhibit cell body VSCC function (evoked increase of intracellular calcium in neocortical neurones) by acting at both intracellular and extracellular sites. 6. The different 'sidedness' of action of emopamil and verapamil on nerve terminal VSCC function and/or the preferential inhibition of cell body VSCC function by emopamil may at least partially explain the relatively greater neuroprotective efficacy of emopamil in experimental models of ischaemia.

Functional status and health status.

Functional status assessment originated in clinical practice in rehabilitation. Health status assessment, a growing part of health services research, grew from the need to survey the health of large populations. In spite of many common interests, the two fields have had little cross-fertilization. The origins and current status of health status measurement are described, including examples of the most frequently used instruments. Conceptual and methodological issues shared by the two fields are examined with the aim of determining what might be of value to rehabilitation. Health-related quality of life provides a conceptual framework that could broaden the rehabilitation perspective. Health status measures may not be appropriate for clinical management but might be useful as quality of care and outcome indicators.

omega-Grammotoxin blocks action-potential-induced Ca2+ influx and whole-cell Ca2+ current in rat dorsal-root ganglion neurons.

Field-potential stimulation of rat dorsal-root ganglion (DRG) neurons evoked action-potential-mediated transient increases in intracellular free calcium concentration ([Ca2+]i) as measured by indo-1-based microfluorimetry. Field-potential-evoked [Ca2+]i transients were abolished by tetrodotoxin, and their dependence on stimulus intensity exhibited an abrupt threshold. omega-Conotoxin GVIA (omega-CgTx, 100 nM) inhibited action-potential-mediated Ca2+ influx by 79%, while nitrendipine (1 microM) had little effect. omega-Grammotoxin SIA (omega-GsTx, 267 nM), a peptide toxin purified from the venom of the tarantula spider, Grammostola spatulata, blocked action-potential-mediated Ca2+ influx as effectively as did omega-CgTx, suggesting that omega-GsTx blocks N-type Ca2+ channels. In contrast to block by omega-CgTx, the block produced by omega-GsTx reversed upon washout of the peptide. omega-GsTx (270 nM) blocked 80%, and omega-CgTx (1 microM) blocked 64%, of whole-cell Ca2+ current (ICa) elicited by step depolarization to 0 mV from a holding potential of -80 mV. omega-GsTx completely occluded inhibition of ICa by omega-CgTx. However, when applied after omega-CgTx, omega-GsTx produced an additional inhibition of 27%, indicating that omega-GsTx also blocked a non-N-type Ca2+ channel. BayK8644 (1 microM) elicited an increase in ICa in the presence of maximally effective concentrations of omega-GsTx, suggesting that omega-GsTx does not block L-type channels. Thus, omega-GsTx displays a selectivity for Ca2+ channel subtypes which should prove useful for studying Ca2+ channels and Ca(2+)-channel-mediated processes.

ICI 206,970: a novel calcium channel blocker with eukalemic diuretic activity.

ICI 206,970 is a novel eukalemic diuretic from the aminomethylphenol pyrazine series which exhibited a calcium antagonist profile. The isolated rat aorta evaluation and dihydropyridine ligand [3H]-PN 200-110 binding studies demonstrated that ICI 206,970, like verapamil and nifedipine, inhibits vascular smooth muscle tone by inhibiting voltage-sensitive calcium channels. ICI 206,970 produced dose-related hypotensive, negative chronotropic, dromotropic, and coronary vasodilator responses after i.v. injection in anesthetized dogs. ICI 206,970, similar to calcium channel blockers and dissimilar to diuretics, produced an acute antihypertensive effect in spontaneously hypertensive rats (SHR), and significant protection against the development of myocardial hypertrophy in SHR after chronic oral treatment for 28 consecutive days. It is concluded that ICI 206,970 is a calcium channel blocker in addition to its novel eukalemic diuretic property.

Isolation and pharmacological characterization of omega-grammotoxin SIA, a novel peptide inhibitor of neuronal voltage-sensitive calcium channel responses.

omega-Grammotoxin SIA, a peptidergic blocker of voltage-sensitive calcium channel (VSCC) responses, was purified from Grammostola spatulata (tarantula spider) venom by reverse phase high performance liquid chromatography. Protease-sensitive biological activity was monitored by determining the inhibition of K(+)-stimulated influx of 45Ca2+ into rat brain synaptosomes. Electrospray mass spectrometry indicated an average molecular mass of 4109.2 Da for the native peptide. Chemical reduction of omega-grammotoxin SIA indicated the presence of three disulfide bridges. Primary sequence data confirmed the existence of six cysteine residues and 36 residues in total, with an average theoretical molecular mass of 4109.7 Da for the amidated carboxyl-terminal species. The biological profile of omega-grammotoxin SIA indicated virtually complete blockade of presynaptic vertebrate N-type as well as P-type VSCC responses. Specifically, omega-grammotoxin SIA caused a concentration-dependent and virtually complete inhibition of K(+)-evoked influx of 45Ca2+ into either rat or chick brain synaptosomes. Similar inhibition profiles were generated for the inhibition of release of either D-[3H]aspartate or [3H]norepinephrine from rat hippocampal or [3H]norepinephrine from chick cortical brain slice preparations evoked by K+ depolarization. As reported earlier, omega-grammotoxin SIA did not inhibit 125I-omega-conotoxin GVIA, [3H]PN 200-110, or [3H]desmethoxyverapamil binding to neuronal membrane fragments. To our knowledge, omega-grammotoxin SIA is the first ligand identified to block putative N-channel function without displacement of 125I-omega-conotoxin GVIA. omega-Grammotoxin SIA thus represents a novel vertebrate VSCC antagonist that inhibits neuronal N- and P-type VSCC responses.